(Original post by TurboCretin)
The OP is asking why you feel an outward force when moving with circular motion, and I was supplying an analogous question. I didn't actually say that they were a third law pair; I wasn't saying anything so specific. I was merely drawing attention to the material point that when you stand, the force which imbues you with weight acts downward, yet you only feel the reactionary upward force.
The example you gave was correct but I was really just clarifying that it was not relevant to the discussion at hand. Whilst that analogy works in many situations I think it serves only to confuse when talking about the centrifugal force (which is what we
talking about) because it is not an example of a 3rd law pair. Indeed Newton's 3rd law has got nothing to do with this particular analysis whatsoever.
(Original post by Stonebridge)
I have never mentioned "centrifugal force" other than in reference to your mention of it.
I didn't say it was "purely subjective". I said it was both. (Subjective and objective)
If you read the discussion page for this article, you will see that it is far from definitive. There are, and have always been, disputes over the meaning and interpretation of "centrifugal force" in connection with this type of scenario.
I've contributed to a number of Wiki articles on this topic. (Not under the "Stonebridge" pseudonym.)
The question wasn't about Coriolis Forces and doesn't need to be.
It was simply about what you "feel".
Fictitious forces are fine for purposes of mathematical analysis, but don't help much in answer to this question about the real forces you feel.
As we have both
pointed out, there is only one force you actually feel on you. And this force has its Newton 3 reaction, which we also agree on.
So I'm at a loss as to quite what we are supposed to be disagreeing on.
What we still disagree on is your first post - which was wrong. Let me refresh your memory:
(Original post by Stonebridge)
To add to what Mr M has said, there is also an element of Newton's 3rd law here.
The question is interesting because it asks about what you actually feel.
You feel the centripetal force acting on your body. In turn, your body applies an equal and opposite force on whatever is producing the centripetal force. It is this 2nd force, the Newton 3 reaction to the centripetal force, that is often described as the force you feel is "throwing you outwards" when going in a circular path.
Look at the bolded bit. That sentence must be wrong because the 2nd force you are describing acts on the body you are orbiting, not on yourself. Thus it is impossible that the force you are describing is the one that you are feeling.
In terms of analysis, lets make this simple:
Imagine we have a massive sun with a planet revolving around it. The sun exerts a gravitational force on the planet. The Newton's 3rd law pair to this is the gravitational force of the planet on the sun. Thus the only force on the planet is the centripetal force. The Newton's 3rd law pair is irrelevant because it acts on the sun, not on the planet.
The reason why the planet would 'feel' a force going outwards can be demonstrated by transforming to the frame of reference of the planet and can be found in any decent physics textbook on classical dynamics. A cute way to think of it though is as the force trying to drag the curved path of the orbit back into a straight line, and thus obviously it must be equal and opposite to the centripetal force. This force is
the centrifugal force.
Interestingly, just by browsing through wiki I saw that your misconception is a common and very understandable one:
Another very common mistake is to state that
The centrifugal force that an object experiences is the reaction to the centripetal force on that object.
Clearly, if an object were simultaneously subject to both a centripetal force and an equal and opposite reactive centrifugal force, the resultant force would vanish and the object could not experience a circular motion. The centrifugal force is sometimes called a fictitious force or pseudo force, to underscore the fact that such a force only appears when calculations or measurements are conducted in non-inertial reference frames. However, the term centrifugal force can also be used, in a different meaning, to denote the reaction force to the centripetal force. It is correct to state, for example: A car driving in a curve exerts a centrifugal force on the road
EDIT: But just browsing through wiki, the various different definitions they have of the centrifugal force serve only to confuse things further. When I use centrifugal force I'm referring to the fictitious force.